Mixed‐Valence Copper Selenide as an Anode for Ultralong Lifespan Rocking‐Chair Zn‐Ion Batteries: An Insight into its Intercalation/Extraction Kinetics and Charge Storage Mechanism

Abstract

Environment-friendly and low-cost aqueous zinc-ion batteries (ZIBs) have received considerable attention for large-scale energy storage. However, the low coulombic efficiency and potential safety hazards of Zn-metal anodes severely hinder their practical implementations. Herein, for the first time, mixed-valence Cu 2−x Se is proposed as a new intercalation anode to construct Zn-metal-free rocking-chair ZIBs with a long lifespan. It is found that the introduction of lowvalence Cu not only modify active sites for Zn 2+ ion storage, but also optimizes the electronic interaction between the active sites and the intercalated Zn 2+ ion, leading to a favorable intercalation formation energy (−0.68 eV) and reduced diffusion barrier, as demonstrated by first-principles calculation. Ex situ X-ray diffraction, ex situ transmission electron microscopy and galvanostatic intermittent titration technique measurements reveal the reversible insertion/extraction of Zn 2+ in Cu 2−x Se via an intercalation reaction mechanism. Owing to the rigid host structure and facile Zn 2+ diffusion kinetics, the Cu 2−x Se nanorod anode shows an enhanced coulombic efficiency (above 99.5%), outstanding rate capability and excellent cycling stability. The as-fabricated Zn x MnO 2 ||Cu 2−x Se Zn-ion full battery exhibits an impressive electrochemical performance, particularly an ultralong cycle life of over 20 000 cycles at 2 A g −1. This study is expected to provide new opportunities for developing high-performance rechargeable aqueous ZIBs.

Enhanced Reversible Zinc Ion Intercalation in Deficient Ammonium Vanadate for High-Performance Aqueous Zinc-Ion Battery

“…GITT plots were measured at a current density of 50 mA g −1 to calculate the diffusion coefficients of the zinc ions as shown in Fig. 6 a, b (details supplied in Supporting information) [ 82 , 83 ]. The D Zn values of NVO during both the insertion and extraction processes are within the orders of 10 −10 to 10 −12 cm 2 s −1 , superior to those of NH 4 V 4 O 10 , indicating the fast Zn-ion diffusion ability, which is agreement with the EIS results.…”

In Situ Carbon Insertion in Laminated Molybdenum Dioxide by Interlayer Engineering Toward Ultrastable “Rocking‐Chair” Zinc‐Ion Batteries

“…[35] Very recently, our group reported a novel anode material, mixedvalence copper selenide; it exhibited an ultralong lifespan (over 20 000 cycles at 2 A g −1 ) but its relatively low initial Coulombic efficiency (66.0% at 0.2 A g −1 ) was unsatisfactory. [36] Consequently, it is desired to develop advanced anode materials with the advantages of high capacity, high initial Coulombic efficiency, stable host structure, and long-term lifespan.…”

Interfacial Kinetics Regulation of MoS2/Cu2Se Nanosheets toward Superior High‐Rate and Ultralong‐Lifespan Sodium‐Ion Half/Full Batteries

“…In the high-resolution spectrum of Cu 2p (Figure 1c), the two strong signs located at 932.6 and 952.4 eV are corresponding to the Cu 2p 1/2 and Cu 2p 3/2 of Cu + , respectively. [26,27] In the Figure 1d, the spectrum of Se 3d can be deconvoluted into two peaks of Se 3d 3/2 (55.2 eV) and Se 3d 5/2 (53.4 eV). [28,29] Moreover, the spectrum of Mo 3d is split into four peaks (Figure 1e); the two main peaks located at 232.3 and 229.2 eV are assigned to Mo 4 + 3d 3/2 and Mo 4 + 3d 3/2 in MoS 2 , while the peak at 226.3 eV is S 2 s in MoS 2 .…”